The present inventions relate to an illumination light control apparatus for an LED (Light Emitting Diode) light-emitting device. The present invention also relates to an illumination system including the illumination light control apparatus an LED illumination apparatus.
When the color temperature of the light from any conventional illumination equipment such as incandescent lamps and fluorescent lamps for illumination of the room was made adjustable, the color temperature was controlled by switching on/off between a high color temperature light source such as a halogen lamp and a low color temperature light source such as an incandescent lamp both installed in the same room.
A wide range illumination apparatus such as the stage lighting, in which incandescent bulbs are used as light sources, the hue and the color temperature are adjusted by using various optical filters, since, the color of the illumination light and the color temperature of the white color are important direction factors under the stage lighting.
In recent years, LED light sources such as LED bulbs become popular and are applied to the illumination use in place of the conventional illumination equipment such as incandescent bulbs. Since the feature of the LED's as light sources is their lower power consumption and longer life than those of incandescent bulbs and fluorescent lamps, it is desired to develop the control system for control the hue and the color temperature for white LED's.
As a prior art of this invention, a circuit in which alternative voltage is supplied to both ends of a pair of LED's or a pair of LED strings (including a plurality of LED's connected in series) was already known as referred to as, for example, in Patent Documents 1, 2, 3.
As further example of prior art of this invention, it was also known an LED driver circuit which drove two LED strings connected anti-parallel each other, wherein the timing control is performed as referred to as in, for example, Patent Document 4. The driver circuit independently controls the conduction period of each positive half waves and negative half waves of AC power supplied to the LED strings.    [Patent Document 1] U.S. Pat. No. 6,412,971 (FIG. 23, FIG. 25, FIG. 26)    [Patent Document 2] Japanese Patent Application Laid-open No. 2002-281764 (FIG. 1)    [Patent Document 3] Japanese Patent Application Laid-open No. 2005-513819 (PCT) (FIG. 2, FIG. 3)    [Patent Document 4] Japanese Patent Application Laid-open No. 2008-218043    [Patent Document 5] Japanese Utility Model Application Laid-open No. 61-138259    [Patent Document 6] Japanese Patent Application Laid-open No. 2008-171984
In the case of control a color temperature of a white light illumination using white LED light sources, the color temperature can be made adjustable by switching on/off the LED light sources having different color temperature.
However, if luminance (amount of the light emitted) and chromaticity (hue (color phase), color temperature) become possible to can be made variable by adjusting a driving current supplied to a single LED illumination apparatus, the LED illumination apparatus can appeal to a wide range of consumers.